#define NO_OPTIONS_OFFSET 5

struct tcpheader {
 unsigned short int src_port;
 unsigned short int dest_port;
 unsigned int seq_num;
 unsigned int ack_num;
 unsigned char th_x2:4, offset:4;
 unsigned char flags;
 unsigned short int window;
 unsigned short int checksum;			// autofilled if set to zero
 unsigned short int urgent_pointer;
};

